请老师看看，可以改进优化吗？

来源：7-2 编程练习

光aaaaand影

2019-08-31 14:58:22

<!DOCTYPE html>
<html>

<head>
    <title></title>
    <style type="text/css">
    html,
    body {
        margin: 0;
        padding: 0;
    }

    div:not(:nth-of-type(2)) {
        width: 500px;
        height: 100%;
        background-color: #a0e4ff;
        margin: 0 auto;
    }
    /*ul默认有外边距*/

    ul {
        width: 300px;
        height: 100%;
        background-color: #ecc7ea;
        list-style: none;
        /*清除默认边距*/
        margin: 0;
        padding: 0;
        margin: 20px auto;
        margin-bottom: 30px;
    }

    li {
        width: 200px;
        height: 30px;
        line-height: 30px;
        margin: 30px auto;
        background-color: #cdffc0;
    }
    </style>
</head>

<body>
    <div id="box">
        <button id="btnAdd">添加元素</button>
        <button id="btnRemove">删除元素</button>
        <ul id="list">我是ul
            <li>我是li1</li>
            <li>我是li2</li>
            <li>我是li3</li>
        </ul>
    </div>
    <script type="text/javascript">
    //此处填写代码
        var btnAdd=document.getElementById('btnAdd'),
            btnRemove=document.getElementById('btnRemove'),
            lis=document.querySelectorAll('li');
        for(var i=0;i<lis.length;i++){
            // (function(){
                lis[i].onmouseover=function(){
                    this.style.backgroundColor="blue";
                };
                lis[i].onmouseout=function(){
                    this.style.backgroundColor="hotpink";
                }
            // })(i)
        }
        var liAll=document.getElementsByTagName('li');
        var list=document.getElementById('list');
        
        btnAdd.onclick=function(){
            var li=document.createElement('li');
            li.appendChild(document.createTextNode('我是li'+ ++liAll.length));
            list.appendChild(li);
            console.log(list);
        };
        btnRemove.onclick=function(){
            list.removeChild(list.lastElementChild);
        }
    </script>
</body>

</html>

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